2 BULLETIN 420, U. S. DEPARTMENT OF AGRICULTURE. 
DESCRIPTION OF EXPERIMENTAL APPARATUS. 
In order to conduct cooling experiments with forced-air circulation 
on a small scale, an insulated box 10 feet 6 inches high, 5 feet wide, 
and 4 feet Sh inches deep was constructed. The box was insulated 
by a 4-inch wall of sawdust, and inside it was built a platform 2 feet 
2 inches fr&ta. the floor, composed of movable sections each the size 
of the bottom of a milk-bottle crate. The plan of this box, together 
with the blower set and arrangement of piping, is shown in figure 1. 
The blower set consisted of a steel-blade fan of a capacity of 2,000 
cubic feet a minute at normal speed, and was operated by a 125-volt 
direct-current, shunt -wound, open-type, variable-speed motor of 1^ 
Fig. 1.— General arrangement of cooling apparatus. 
horsepower. The blower was connected to the box by pipes of gal- 
vanized iron of 14-inch diameter, which were so arranged that air 
could be forced in at the bottom of the box and out at the top, or the 
reverse; that is, in at the top and out at the bottom. This was made 
possible by two inlet and outlet pipes connected with the box and 
controlled by a system of dampers. 
Most of our experiments were conducted during the winter months; 
consequently the outside air was sufficiently cold for the cooling 
process. As may be seen in the figure, the blower drew outside air 
through pipe B and forced it into the cooling box. 
